A digital video conversion box (set top box) is a device that connects a television to an external signal source. The set top box is usually equipped with a “transparent transmission” option. When the transparent transmission is selected to be enabled, audio data may be sent by the set top box to the television directly and decoded by the television, in this way, the audio data is decoded directly by the television, and a better tonal quality effect is achieved; when the transparent transmission is selected to be disabled, the set top box will decode the audio data acquired from an external signal source and then transmit it to the television; when an automatic transparent transmission is selected, the set top box may determine whether to decode the audio data by itself based on extended display identification data (Extended Display Identification Data, EDID) information read from the television, if the EDID information does not include an audio format to which the audio data to be transmitted belongs, the set top box will try to decode the audio data and then transmit it to the television, if the EDID information includes an audio format to which the audio data to be transmitted belongs, the set top box transparently transmits audio data to the television.